Dishwashers comprise a filter at a bottom of a washing compartment for filtering soil from process water being recirculated in the dishwasher by means of a circulation pump. This is undertaken in order to prevent dirty process water from being recirculated and sprayed onto goods to be washed. When an excess amount of soil adheres to the filter, the filter becomes clogged and the water will ultimately not pass through the filter. It may thus be desirable to detect filter clogging such that the filter can be cleaned in order for the dishwasher to reach its full washing capability.
International patent application having publication number WO 2005/089621 discloses a dishwasher and a method of controlling the dishwasher, where effects influencing washing performance negatively such as for example filter clogging are identified by detecting current drawn by a circulation pump of the dishwasher. A disadvantage of the approach set forth in WO 2005/089621 is that detection of current drawn by the circulation pump may result in an erroneously taken decision on whether the filter is clogged or not; a reduced load on the circulation pump could just as well be a result of an insufficient amount of process water in the washing compartment of the dishwasher in which case a too small amount of process water will be circulated in the dishwasher resulting in a low process water flow through the circulation pump. Thus, the amount of current drawn by the circulation pump could indicate filter clogging when the problem in fact is that the washing compartment contains an insufficient amount of process water, which is highly undesirable.